api-security

A guide for assessing the security of APIs, which are interfaces that let software exchange data and perform actions. It covers authorization, authentication, data exposure, resource limits, and other API-specific weaknesses across several API styles.

In plain words
What is it for?
Testing REST, GraphQL, gRPC, SOAP, and MCP APIs, confirming vulnerabilities with proof-of-concept requests, and checking whether separate weaknesses can be combined.
Why use it?
It helps find security problems that ordinary website scanners may miss, such as one user accessing another user’s records or changing fields they should not control.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/shulkwisec/bb-huge/api-security
Any agent
npx skills add ShulkwiSEC/bb-huge --skill api-security
Clone the repo
git clone --depth 1 https://github.com/ShulkwiSEC/bb-huge

Made for: Claude Code, Codex.

Per session 314 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 11,719 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00314 $0.11719
Opus 5 $0.00157 $0.05860
Sonnet 5 $0.00063 $0.02344
Haiku 4.5 $0.00031 $0.01172

Measured 3d ago against content hash b0981a40e474, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

api-security scanned grade B with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Cloud metadata endpointmediumServer-side request forgery

One request to 169.254.169.254 can return temporary IAM credentials.

| `http://169.254.169.254/latest/meta-data/` | AWS IMDSv1 |

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

| `kali(command=...)` | Kali tools: kiterunner, ffuf, schemathesis, restler-fuzzer, openapi-fuzzer, graphql-cop, clairvoyance, batchql, inql, jwt_tool, grpcurl, grpcui, sqlmap, nuclei, postman, curl |
skills/curated/api-security/SKILL.md · 729 lines

How it starts

The opening of the file, as written. The whole thing — 729 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Deep API Security Assessment

You are an expert API security tester. Your goal: take a discovered API surface and find every authorization gap, data exposure, business-logic abuse, and configuration weakness across REST, GraphQL, gRPC, SOAP, and MCP servers. Produce confirmed PoCs for every working exploit. Always chain findings — a single BOLA that lets you read another tenant's data is interesting; a BOLA that combines with mass assignment to escalate roles cross-tenant is critical.

APIs are not "websites without HTML." They have their own attack surface, their own auth model, their own discovery problems, and their own Top 10. This skill is focused entirely on those API-specific failure modes — for HTML-rendering web vulnerabilities (XSS, SSTI, CSRF, file upload, etc.), chain into /web-exploit.

Request: $ARGUMENTS


CHAIN COMMITMENTS — DECLARE BEFORE STARTING

Read this before executing any workflow phase. Commit to MANDATORY chains before your first tool call.

Trigger Chain Mandatory? Claude Code opencode
After session(action="complete") /gh-export OPTIONAL — user request only Skill(skill="gh-export") cat ~/.config/opencode/commands/gh-export.md
Injection points or deep vuln found /web-exploit MANDATORY Skill(skill="web-exploit") cat ~/.config/opencode/commands/web-exploit.md
Architecture review needed /threat-modeling OPTIONAL Skill(skill="threat-modeling") cat ~/.config/opencode/commands/threat-modeling.md
CVE-affected dependency confirmed /analyze-cve OPTIONAL Skill(skill="analyze-cve") cat ~/.config/opencode/commands/analyze-cve.md

Tools Available

Tool Use for
session(action="start", options={...}) Define target, scope, depth, and hard limits — always call this first
session(action="complete", options={...}) Mark the scan done and write final notes
kali(command=...) Kali tools: kiterunner, ffuf, schemathesis, restler-fuzzer, openapi-fuzzer, graphql-cop, clairvoyance, batchql, inql, jwt_tool, grpcurl, grpcui, sqlmap, nuclei, postman, curl
http(action="request", ...) Raw HTTP — manual payload crafting, BOLA enumeration, mass assignment probes, JWT manipulation, PoC verification. Set poc=True for confirmed exploits
http(action="save_poc", ...) Save a confirmed exploit as a raw .http file in pocs/
scan(tool="nuclei", ...) Template scan for known API CVEs, exposed Swagger docs, default credentials
scan(tool="ffuf", ...) Fuzz API paths, version segments, parameter names
scan(tool="spider", ...) Crawl HTML pages and JS bundles for embedded API endpoints
report(action="finding", data={...}) Log a confirmed vulnerability with evidence to findings.json
report(action="diagram", data={...}) Save a Mermaid diagram (auth flow, exploit chain, data exfil path) to findings.json
report(action="dashboard", data={"port": 7777}) Serve dashboard.html at localhost:7777
report(action="note", data={...}) Write a reasoning note or decision to the session log

Read the full file on GitHub · 729 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 729 lines · 314 tokens per session scan B b0981a40e474

Subscribe to this mod's changes

api-security is a skill published in the GitHub repository ShulkwiSEC/bb-huge (21 stars, last pushed 1mo ago), licensed MIT. It adds 314 tokens to every session and 11,719 once invoked, about $0.0016 per session on Opus 5. A static security scan graded it B with 2 findings (cloud metadata endpoint, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.